Customers often ask: How can strong magnets be brought on board? What measures do we need to take? What are the requirements for packaging? Today we will explain these questions in detail.
As the weak stray magnetic fields interfere with both the aircraft's navigation system and control signals, the International Air Transport Association (IATA) classifies magnetic cargo as Class 9 dangerous goods, which must be restricted at the time of receipt and shipment. Therefore, some air cargoes with magnetic materials are now required to undergo magnetic inspection in order to ensure the normal flight of the aircraft. Magnetic materials, audio materials and other instruments containing magnetic accessories are subject to magnetic testing.
The magnetic field strength of magnetized materials must be measured using measuring devices having a sensitivity sufficient to measure magnetic fields greater than 0.0398 A/m (0.0005 gausses) within a tolerance of plus or minus 5% or with a magnetic compass sensitive enough to read a two-degree variation, preferably in 1-degree increments or finer. Methods of determining if a magnetized article meets the definition of a magnetized material include:
Method 1— When an oersted meter is used, it is placed on one of two points positioned 4.6 m (15 ft) apart and located in an area that is free from magnetic interference other than the earth's magnetic field. The oersted meter is then aligned with the second point and “balanced” to a zero reading. The magnetic article is then placed on the other point and the magnetic field strength is measured by reading the meter while rotating the package 360 degrees in its horizontal plane. If the maximum field strength observed is 0.418 A/m (0.00525 gausses) or less, the article is acceptable for air transport. When the maximum field strength exceeds 0.418 A/m (0.00525 gausses) shielding should be applied until a reading of 0.418 A/m (0.00525 gausses) or less has been attained.
Method 2— When a magnetic compass is used as a sensing device, it should be placed on one of two points positioned 4.6 m (15 ft) apart which are aligned in an East/West direction and in an area that is free from any magnetic interference other than the earth's magnetic field. The packaged item to be tested is placed on the other point and rotated 360 degrees in its horizontal plane for indication of compass deflection. When the maximum compass deflection observed is two degrees or less, the article is acceptable for air transport. When the maximum compass deflection of an item exceeds 2 degrees, shielding must be applied until the maximum deflection is not more than 2 degrees.
If the maximum field strength observed at a distance of 2.1 m (7 ft) is less than 0.159 A/m (0.002 gausses) or there is no significant compass deflection (less than 0.5 degrees), the article is not restricted as a magnetized material.
In order to meet the above requirements for air transport, the magnet needs to be demagnetized for air transport, although it is called demagnetization, in fact, it is not demagnetization of the magnet, but through special shielding packaging, so that the magnetism of the package can be measured externally to meet the requirements of air safety transport. Shielding packaging will generally use high magnetic conductivity materials, cold-rolled sheets, and galvanized sheets, etc. if the number of magnetic materials to pack several layers. The magnetic conductivity of high permeability materials is very high, according to the Faraday electric cage principle, the magnetic field is mainly circulated in the box after packaging, leaking out even less, shielding packaging outside and then packed in cartons or wooden boxes, and finally need to issue a magnetic test report.
1. Magnetron and illumination meter and other instruments, and devices, the opposite magnetic poles must be placed, relative.
2. Permanent magnet material must be installed with magnetic armature or shielding to prevent magnetic field caused by the deviation of the compass instrument.
3. Each package of magnetic material must be properly marked and labeled in accordance with the provisions of Chapter 7 of the IATA Dangerous Goods Regulations.
4. Ensure that the magnetic field strength measured at 4.6 meters (15 feet) from the surface of the package does not exceed 0.418A/m (0.00525GS) before the shipment
5. It is recommended that wooden boxes be externally packed for large cargo.
This is the first one.